“Sialo-sugar chain” is a generic term for sugar chains having a sialic acid at the non-reducing end. Sialo-sugar chains are an important constituent of glycolipids, gangliosides, and various glycoprotein sugar chains. Sialo-sugar chains have various functions, such as control of essential phenomena in vital activities such as intercellular recognition, differentiation, and proliferation, as well as association with canceration, virus infection, etc. For example, it has been elucidated that many sialo-sugar chains are present in cancer-related carbohydrate antigens. It has also been elucidated that infection with an influenza virus occurs when a sialylgalactose moiety (a disaccharide consisting of sialic acid and galactose bonded together) expressed on the host cell surface serves as a scaffold.
Sialo-sugar chains, which are involved in such various phenomena, are applicable in a wide variety of fields. Therefore, there is a need to develop a sialo-sugar chain having a structure that can be utilized in many fields.
Furthermore, methods for production or purification of sialo-sugar chains are usually complicated. Therefore, in the production or purification of sialo-sugar chains, extremely high levels of skill, expensive equipment and reagents, and harmful reagents are required. Therefore, there is a need to develop a method for easily and efficiently mass-producing a sialo-sugar chain.
A method comprising reacting lactose and sialic acid in the presence of Arthrobacter ureafaciens-derived neuraminidase is known as an example of producing a sialo-sugar chain (Non-patent Literature (NPL) 1). However, this production example is unsatisfactory in terms of easily and efficiently producing a sialo-sugar chain. One specific disadvantage of this method is the production of a plurality of sialo-sugar chains that are different in the non-reducing end of lactose to which the sialic acid of the sialo-sugar chain bonds. Another disadvantage is that sialo-sugar chains produced according to this production example are those comprising sialic acid and lactose simply bonded together, and they are difficult to apply in many fields.